The present invention relates to a variable transmission optical switch, and particularly to a projectile fuze including an optical switch for arming the fuze during projectile launch.
A variable transmission optical switch disclosed in U.S. Pat. No. 3,560,077 to Walter R. Sooy et al. comprises a housing having optical windows for passing light therethrough and containing a light absorbing liquid, and means for moving one of the windows to change the thickness of the liquid layer to vary the light transmission.
Applicant's invention provides a variable transmission optical switch comprising a housing having a pair of aligned optical windows for passing light therethrough and containing a light attenuating gas is the light path, and means for varying the pressure and density of the gas to vary the intensity of the light transmitted. For example, the gas may be contained in the housing at a given pressure and density at which the light attenuation is high, and the gas pressure may be reduced by means of a pressure relief valve in the housing which opens at a predetermined reduced external pressure to reduce the density of the gas. The optical switch may be carried by a projectile fuze launched to a critical altitude at which the relief valve opens and the transmitted light energizes a light sensitive device to arm the fuze. The housing is preferably provided with a piston actuated by inertia during projectile launch to decrease the gas volume and thereby increase the pressure of the gas from an intermediate to a high value.